Signal transducers and activators of transcription-3 (STAT3), a central cytoplasmic transcription factor, is frequently overexpressed and constitutively activated during malignant transformation. The overexpression of STAT3 in melanoma cells is often observed and is suggested to be involved in tumorigenesis and development. In this study, a novel antisense RNA oligonucleotides targeting the STAT3 mRNA was 2'-O-methyl modified with a 3'-butanol tag was designed, and found this uniquely modified strategy dramatic increased the stability of the RNA oligonucleotides. The results showed that the RNA oligonucleotides, namely STT-33 and STT-34, strongly inhibited the target gene expression in the melanoma cells and resulted in increase cell apoptosis. Furthermore, the RNA oligonucleotides could significantly inhibit melanoma cell proliferation and xenografts growth in nude mice. Thus, the novel modified RNA oligonucleotides targeting STAT3 may serve as a useful tool to study the involvement of STAT3 in melanoma and potentially as an anti-cancer agent for melanoma.